The present invention relates to apparatus for processing tobacco, especially to distributors for use in machines for the making of cigarettes or the like. Still more particularly, the invention relates to improvements in apparatus for regulating the level of the upper surface of a supply of tobacco which is confined in a magazine.
Commonly owned patent application of Ser. No. 834,782 filed Sept. 17, 1977 by Heitmann et al., now U.S. Pat. No. 4,185,644 discloses a distributor for cigarette makers wherein an endless conveyor transfers tobacco from a main magazine into an upright duct and a refuser in the form of a paddle wheel equalizes the batches of tobacco which are transported by the conveyor toward the inlet of the duct. This invention relates to improvements in apparatus of the type disclosed in the application of Heitmann et al.
The aforementioned duct constitutes a relatively small intermediate magazine whose outlet discharges tobacco (or from whose outlet tobacco particles are withdrawn) for conversion into a relatively wide carpet which is thereupon subjected to a classifying action to segregate heavier particles and converted into a rising or descending shower preparatory to the formation of a continuous narrow stream. The stream is trimmed, if necessary, prior to draping into a web of cigarette paper or other suitable wrapping material. The provision of a duct between the main magazine and the carpet forming station is desirable because the volume of tobacco in the duct can be readily maintained within a predetermined range which is best suited for withdrawal of tobacco at a constant rate and in a predictable state. Such withdrawal is a prerequisite for the formation of a homogeneous carpet which, in turn, can be converted into a homogeneous tobacco stream. The duct has been found to contribute significantly to homogenization of the body of tobacco which is treated on its way into the stream forming channel of a cigarette maker or the like. It is important and desirable that the density of tobacco at the outlet of the duct be as constant as possible because this determines the quality of the tobacco stream. To this end, the duct is provided with a level detector which monitors the level of the upper surface of the supply of tobacco in the duct and transmits appropriate signals for adjustment of the mechanism which feeds tobacco into the inlet of the duct. The signals which are transmitted by the level detector can be used to accelerate or decelerate the conveyor which delivers tobacco from the main magazine into the duct in such a way that the rate of feed increases when the upper level, (i.e., the volume) of the tobacco supply sinks and vice versa. Alternatively, and as disclosed in French Pat. No. 1,273,931, the level detector can start or arrest the motor for the tobacco feeding mechanism.
In many instances, the duct is relatively wide as considered in one transverse direction and very narrow as considered in the other transverse direction. Otherwise stated, the duct has relatively wide front and rear walls but narrow side walls which are disposed at the lateral ends of and extend between the front and rear walls. In such ducts, the height of the supply of tobacco often varies, as considered in a direction from one side wall toward the other side wall, i.e., the upper surface of the supply of tobacco in the duct may slope from one side wall toward the other side wall or it may have a peak somewhere between the side walls and two downwardly sloping portions extending from the peak toward the side walls.
The primary reasons for such unequal filling of the duct are the size, shape, weight, moisture content and other characteristics of tobacco which is drawn from the main magazine. The body of tobacco in the main magazine is not a homogeneous mass; it comprises particles of dust, relatively large fragments of ribs, and clumps of interlaced shreds. The conveyor (e.g., an endless carded belt) which removes tobacco from the main magazine is incapable of withdrawing tobacco at a uniform rate, i.e., the quantity of tobacco along one marginal portion of such conveyor often exceeds the quantity of tobacco which is adjacent to the other marginal portion. Consequently, certain portions of the conveyor entrain large batches of tobacco whereas other portions entrain much smaller quantities. Furthermore, batches of tobacco which contain large quantities of dust or so-called shorts are likely to form dense parts of the supply of tobacco in the duct. The presence of accumulations of tobacco dust in the main magazine is due to the fact that dust is collected in several areas of a cigarette maker and the accumulated dust is segregated from the conveying medium (normally air flowing to a suction generating device) and returned into the main magazine. Still further, unequal distribution of tobacco in the dust (so that the upper surface of tobacco supply slopes toward the one or the other side wall of the duct) can be caused by improper adjustment of paddles on the paddle wheel or a like refuser which is used to remove the surplus from the transfer conveyor.